Technical Field
The technical field presented herein is directed toward an optical fiber sensor including at least one pair of optically coupled photonic crystal slabs separated by a length of optical fiber.
Technical Background
Fiber Bragg Grating sensors are traditionally the optical sensor of choice in most situations. Fabrication of these traditional sensors requires removal of the optical fiber cladding and modification of the optical fiber core, and subsequent replacement of the fiber cladding. Newer methods have been developed that allow modifications in index of refraction in the fiber without the need for cladding removal yet these construction methods lead to fabrication difficulty and additional cost. Other types of sensors include affixing optical fiber strands onto materials and attempting to look for variations in transmitted light, however, these types of sensors require an optical sending and an optical receiving system tied to opposite sides of the optical fiber strand.
Other approaches look at discontinuities already present along the entire length of an optical glass fiber and use the optical fiber itself as a form of natural Bragg Grating system. The equipment needed to perform this has appeared to be expensive and complex and does not appear to lend itself to allowing other sensors to operate on the same fibers.
In contrast to optical fiber sensors, electrical based sensors and systems are believe to be far too susceptible to such environmental threats, and also none appear to offer single connection to multi-sensor hookups. Optical fiber solutions provide the benefit of being resistant to EMI, RFI, lightning and allow the optical fiber to be used in hazardous environments where electrical based sensors would not optimally function.
Another concept involves creation of a Fabry-Perot Interferometer using TiO2 dielectric mirrors separated by a piece of optical fiber. This type of sensor in essence creates a much larger mirror-to-mirror structure which is similar in function to Micro-Electro-Mechanical Systems (MEMS) based Fabry-Perot Interferometers. However, the use of TiO2 dielectric mirrors is limited in its use to only narrow spectrums of operating light wavelengths.
There is a need for an optical fiber based strain gauge equivalent to Fiber Bragg Grating type design, but with the advantages of emitting light wavelength selectivity, operation with or without laser sources, and interoperation with multiple strain sensors on same optical fiber. It is with respect to these and other considerations that the disclosure herein is presented.